Monday, May 21, 2012

Mulching for (No) Rain

Since naturalizing in central Texas, I have become obsessed with rain – if we will get any, when we will get any, and, if so, how much we will get.  I have also developed a superstition about how to not to screw up our chances for rain.  It started with the simple and annoying observation that, if the rain chances for a given day were in the middle of the road, say 50% chance of thunderstorms, and my plants needed to be watered, the chances for rain would plummet to about 5% the minute that I decided not to water because rain was on the way.  So I learned, in my early years of Austin gardening, that if the soil was dry and the rain chances were anything less than "flash flood warning starting at noon today," I had better water.  Because to be prepared for no rain was the best way to encourage those middling chances of rain.

Using the same logic, the best way to attract a rainy season to town is to be prepared for weeks of heat and drought.  Which means that my job in the early summer, after the tomato, pepper, eggplant, and okra plants of my hot-season garden have established, is to prepare the garden for the onslaught of summer drought.  Because to be prepared for early, baking heat is the best way to bring thunderstorms to May and June, which can be the rainiest months of the year here in Austin, where a "rainy season" can happen at any time of year, for any number of weeks, or can just as easily disappear, at any time, for any number of months.

I prepare for drought by mulching, or covering the garden soil with a thick layer of leaves, stems, or wood chips.  I look forward to mulching day through March and April, during the seed planting, transplanting, daily watering, and weeding, because mulching day is like graduation day for my plants.  After mulching I still love them and care for them, but my role is changed.  If the rains don't come, I water twice a week, in the dark of the night, by turning on a soaker hose and disappearing into the climate-controlled house while a timer runs.  If the rains do come, then I am really not needed in the garden except to harvest fruits, which my plants make all on their own, in the bright light of Texas summer.  So I love the tucked-in and ready-to-take-care-of-itself look that the garden has just after it has been mulched.

The mulching material that I use varies depending on the season, the type of garden bed, and what I have on hand.  For establishing new garden beds, which requires a deep mat of heavy mulch to kill the weeds and limit the unkillable Bermuda grass, so that its greenery is reduced and its roots are easily dig-out-able, I use lawn clippings.  Lawn clippings are ugly and moldy, but, over time, as the layers pile on, they make an effective barrier against weeds that eventually breaks down into compost, improving the future garden soil.  More importantly, the depth and thickness of a mat of lawn clippings ensures that the soil beneath is heavily insulated from the heat and dry of the air above, creating a moist, cozy environment for the bacteria, fungi, and insects of the soil, who in turn are the real creators of that future garden soil.

On my garden pathways and around my perennials, I use cedar mulch.  It's inexpensive and attractive, and I like the smell.  As a big fan of trees being left standing, I do worry about using wood mulches, but as far as I can tell, the cedar mulch made by Austin Wood Recycling is made by shredding cedar (Juniperus ashei) trees that are cleared from overgrown land.  Given that cedar trees are abundant to the point of being invasive in central Texas, I don't mind the idea of those trees being torn down and shredded for mulch, though I do wish they were being torn down to make room for a native grassland instead of a housing development.  In any case, cedar mulch keeps my front-yard garden looking neat around the edges and it is long-lasting.  The only downside to cedar mulch is that it is as attractive to the neighborhood cats as it is to me.  Apparently, if you're a cat, wild or allowed to roam, to whom my street is home, then my garden is the place to shit.  When I lost a couple of baby plants to an over-exuberant feline digger this spring, I began to reconsider: maybe it's time to switch to gravel mulch for the perennial beds.

In the winter, or when I have them, I use fallen leaves.  My backyard produces a good pile of leaves every December, a mix of post oak, cedar elm, and hackberry.  Still, I always think that I could use a lot more leaves, because of which I have a mental map of whose lawns along my usual driving routes have the best mix of leaves and often find myself, around the end of the year, wondering about the contents of other people's yard-waste bags.  I pile the raked leaves around my fall greens, just after they've passed the baby greens stage, or around the broccoli-family transplants after they have established.  I usually save the last raking of the season, the January (or, this year, February) leaf pile, to be used at the end of the hot season, to be the mulch-on-top-of-the-mulch that puts the garden to bed for the hottest months of the year.

My favorite mulch, the mulch that I use for my hot-season vegetable garden, is alfalfa hay.  Alfalfa isn't technically a hay, because alfalfa itself is not a grass but a broad-leafed plant in the Pea Family, but, because it comes in heavy bales and is called "hay" by horse people, I think of it as alfalfa hay.  But the fact that it is not hay is actually quite important to my garden.  The first hay that I tried to use as mulch for my community garden plot, in my first summer as a Texas gardener, was grass hay.  Where I grew up, in western Oregon, grass hay was common stuff, so I was surprised when nobody in Austin had heard of grass hay.  Instead, I was directed to something called "coastal hay," which seemed to be the Texas equivalent of grass hay.  I found the coastal hay to be expensive and crappy compared to the grass hay that I had known, but I put it on my garden anyway.  My plants didn't die that year, but they didn't thrive either, and it took the soil a couple of seasons to get back to what it had been.

During which time I learned a couple of things about hay.  First, it turns out that the Willamette Valley of Oregon is the world center of grass seed production.  Long, rainy, mild springs produce the best grass hay in the world with minimal chemical input.  So my views on hay quality and availability are heavily skewed by memories of hauling in bales of hay from the neighbor's field in June and feeding fine-stemmed, sweet-smelling flakes of grass hay to the horses all winter.  Second, and more importantly, Texas coastal hay is heavily sprayed with broad-leafed herbicides, which are poisonous to garden plants.  The moral of the story is that coastal hay is poison for your garden.

Once I was aware of the perils of using true hay in Texas, I switched to alfalfa, which worked so well that it has become a yearly ritual to go to the farm supply store to buy a couple of bales.  At the end of April, once the okra has been thinned, and the beds have been weeded one final time, and the soaker hoses are in place, I tear apart flakes of alfalfa and stuff handfuls of the scratchy stems between my plants, creating a thick, unbroken layer of mulch.  If I am lucky, thunderstorms follow mulching day, and the heavy rains seal the alfalfa into place like a heavy, woven crust over the garden.  Alfalfa mulch stays in place, through rain or shine, better than any other mulch I have used, and for that alone it is a great mulching material.  But that is just the beginning of its utility.  Alfalfa is also perfect for my hot-season garden in that it lasts all season but, after several months on the soil, breaks down just as readily.  In fact, I have found that if I cover the alfalfa with a layer of leaves as I remove the spent garden plants in August, in effect mulching the mulch, then, when the fall rains come, the alfalfa beneath the leaf mulch will compost quickly, largely disappearing into the soil by the time of fall planting.

When alfalfa breaks down into the soil, it feeds the soil.  This is true of all mulches – except for gravel mulch, of course, unless you think in geologic time – they eventually break down and add organic matter and nutrition to the soil.  But, while shredded wood can actually rob the soil, temporarily, of nutrients, and dead leaves add mainly micronutrients and humic acid to the soil, alfalfa is high in nitrogen, which is a primary soil nutrient needed by plants.  In fact, "alfalfa meal" is often one of the first ingredients in organic fertilizers, providing the nitrogen part of the N-P-K kick. And that is the real reason, aside from the satisfaction of heaving a bale of hay, that I love to use alfalfa to mulch my summer garden.  Every time I buy a bale of alfalfa, I feel clever knowing that this year's mulch is also next year's fertilizer.

Here is the final secret about mulching that the rain gods don't need to know:  To mulch is also to prepare the garden for a rainy summer.  Just as a thick layer of mulch protects the soil from evaporation, it also protects the soil from flooding.  In the midst of a downpour, water reaches the garden bed more gently, only after flowing around and through the many layers of leaves and stems that make up the mulch, so the soil beneath is much less likely to be carried away.  Plus, mulch reduces splashing, so that the undersides of the leaves of my eggplant, tomato, pepper, okra, and basil plants don't get coated in mud during a storm.  Because of this, the plants are less prone to the fungal diseases that ride around in mud splashes, and they stay cleaner.

So every season I mulch, in preparation for heat and drought, but also in hopes of a rainy season.  I mulch to protect the soil this season, to improve the soil next season, and to feed the soil the season after next.  I mulch because no other garden practice is so cheap and easy, with so many benefits to the soil.  The soil that is the basis of this entire operation.


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